Linear carboxy-functional organosiloxanyl derivatives and the use thereof for the treatment of the surfaces of leather

ABSTRACT

The invention relates to linear carboxy-functional organosiloxane compounds of the general formula (I)  
                 
 
     in which  
     a is from 1 to 200,  
     R 1  are identical or different aliphatic or aromatic hydrocarbon radicals and  
     R 2  is —(Y)[O(C 2 H 4-b (R 3 ) b O) c (C d H 2d O) e ] f X,  
     and the use thereof for the treatment of the surface of leather.

RELATED APPLICATIONS

[0001] This application claims priority to German application Ser. No.103 04 330.6, filed Feb. 4, 2003, herein incorporated be reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to novel carboxy-functional organosiloxanylderivatives and the use thereof for the treatment of the surface ofleather.

[0004] 2. Description of the Related Art

[0005] Leather left in the natural state is susceptible to dirt andmoisture, owing to its chemical structure and its fibrous composition.As positive as its absorptivity, water absorption capacity andpermeability in clothing and footwear with respect. to the body's ownperspiration may be, this behavior will be assessed negatively under theaction of external moisture.

[0006] An important precondition for the usability of leather clothingin private and commercial use relates to its waterproof or at leastsubstantially water-repellant properties.

[0007] In order to achieve this effect, impregnating agents based onanimal, vegetable and synthetic products have already been used in thepast.

[0008] Owing to their performance characteristics, the synthetic agentshave very substantially become established, in particular thepolysiloxanes in their various modifications.

[0009] Polysiloxanes have a high surface tension with respect to waterand, owning to the greatly reduced adhesion to water, enable itscohesive forces to be fully effective, with the effect that theresulting beads and drops are repelled by the surface.

[0010] In order to increase the purely mechanical and electrostatic (vander Waals) adhesive forces of the polysiloxanes, functional groups, suchas, in particular, carboxyl groups, were incorporated in the molecule.Via these groups, the polysiloxane is strongly bonded by chemical bondsto the fibers of the leather.

[0011] In comparison with the impregnating agents used therein, asubstantial long-term effect could be achieved since the water-repellantprotective layer is less easy to remove by scouring, abrasion or otherexternal mechanical stresses.

[0012] EP-A-0 745 141 describes a process for waterproofing leather andskins in aqueous emulsions and in the presence of emulsifiers withpolysiloxanes carboxy-functionalized in a comb-like manner, in which thecarboxyl groups are bonded to the polymer main chain via spacer groupsin the form of linear or branched C₂-C₄₀-alkylene groups which likewisemay contain hetero atoms or hetero groups.

[0013] EP-A-0 324 345 describes a process for waterproofing leather,skins and leather substitutes, according to which polysiloxanes whichpreferably have terminal carboxyl groups and whose carboxyl groups arepresent in neutralized form are used.

[0014] WO-A-93/22464 describes a -process for waterproofing leather,skins and leather substitutes using sulfosuccinic esters prepared frompolyols and maleic anhydride and sulfites as water repellants, accordingto which alpha-/omega-OH-functional polysiloxanes can also be used aspolyols.

[0015] The water repellant effect of these compounds is, however,furthermore in need of improvement with respect to water repellency,flexibility, abrasion resistance and resistance to extreme externalstresses, as occur in particular in the case of work clothing orprotective clothing used in industrial or military applications or thefootwear used there.

OBJECTS OF THE INVENTION

[0016] It was therefore an object of the present invention to providewater repellants for leather which have improved performancecharacteristics under severe external stresses.

[0017] It is further object of this invention to make apparel leatherwater repellant with full elasticity and softness. In the treatment,instead of a thin film being applied over the leather surface, the waterrepellant penetrates into the leather and surrounds the leather fibers,which thus: remain breathable.

[0018] These objects and others, which will become apparent from theDescription of the Invention are achieved by using linearcarboxy-functional organosiloxane compounds.

DESCRIPTION OF THE INVENTION

[0019] The invention therefore relates to linear carboxy-functionalorganosiloxane compounds of the general formula (I)

[0020] in which

[0021] a is from 1 to 200, preferably 10 to 150

[0022] R¹ are identical or different aliphatic or aromatic hydrocarbonradicals,

[0023] R² is —(Y)[O(C₂H_(4-b)(R³)_(b)O)c(C_(d)H_(2d)O)_(e)]_(f)X,

[0024] where

[0025] Y is an (f+1)-valent, optionally branched hydrocarbon radicalhaving 3 to 12 C atoms,

[0026] b is from 1 to 3,

[0027] c is from 0 to 20,

[0028] d is from 2 to 4,

[0029] e is from 0 to 20,

[0030] f is from 1 to 4,

[0031] R³ is R¹,

[0032] X is C(O)-Z-CO₂H and

[0033] Z is a divalent hydrocarbon radical selected from the groupconsisting of

[0034] where

[0035] g is from 1 to 12;

[0036] R^(a) is alkyl, especially C₁-C₄ alkyl and most especially —CH₃;and

[0037] y is 0 to 4.

[0038] Especially preferred are compounds wherein R^(a) is methyl and yis 1, or those compounds where y is 0; i.e., those compounds wherein thecyclohexyl ring is unsubstituted (no R^(a) group).

[0039] The invention furthermore relates to the use of linearcarboxy-functional organosiloxane compounds of the general formula (I)for the treatment of the surface of leather.

[0040] Preferred linear carboxy-functional organopolysiloxanes are thosewherein R¹ is a C₁-C₆ hydrocarbyl group, with alkyl such as methyl andethyl being more preferred, or is a C₆ to C₁₂ aromatic group such asphenyl. Especially preferred groups for R¹ are H and/or methyl. Otherpreferred linear carboxy-functional organopolysiloxanes wherein a has avalue from 10 to 2000 or R² is a polyether radical comprising mixedblocks.

[0041] A person skilled in the art is familiar with the fact that. thecompounds are present in the form of a mixture having a distributionsubstantially regulated by statistical laws. The values for the index aare therefore mean values.

[0042] Compounds according to the invention can be prepared in a simplemanner by reacting hydroxy-functional siloxanes of the general formula

[0043] in which

[0044] a is from 1 to 200,

[0045] R¹ are identical or different aliphatic or aromatic hydrocarbonradicals,

[0046] R⁴ is —(Y)[O(C₂H_(4-b)(R³)_(b)O)c(C_(d)H_(2d)O)_(e)]_(f)H,

[0047] where

[0048] Y is an (n+1)-valent, optionally branched hydrocarbon radicalhaving 3 to 12 C atoms,

[0049] b is from 1 to 3,

[0050] c is from 0 to 20,

[0051] d is from 2 to 4,

[0052] e is from 0 to 20 and

[0053] f is from 1 to 4,

[0054] with organic carboxylic anhydrides of the general formula

[0055] in which

[0056] Z is a divalent hydrocarbon radical selected from the groupconsisting of

[0057] where

[0058] g is 1 to 12

[0059] R^(a) is alkyl, especially C₁-C₄ alkyl; and

[0060] y is 0 to 4.

[0061] Examples of substances according to the invention are:

[0062] in which R^(a) may be identical or different and are H or aC₁-C₄-alkyl radical y is 1 to 4 and z is 3 to 12. Especially preferredare those substances where R^(a) is methyl and d is 1. Compound a b c R¹y 1 10 6 0 Me 0 2 20 6 0 Me 0 3 30 6 0 Me 0 4 70 6 0 Me 0 5 20 3 0 Me 06 30 3 0 Me 0 7 30 3 0 Me 0 8 30 6 4 Me 0

[0063] The following synthesis examples serve as non-limiting exampleswhich explain the invention.

EXAMPLE 1

[0064] Addition reaction of hexahydrophthalic anhydride with a linearhydroxy-functional siloxane:

[0065] In a three-necked flask equipped with a coil condenser,thermometer and dropping funnel and a nitrogen connection, 92 g ofhexahydrophthalic anhydride and 908 g of a linear hydroxyfunctionalsiloxane of the general formula (II):

[0066] having a hydroxyl number of 45 mg KOH/g (i.e. a is 29) and aviscosity of 85 mPa.s were mixed in a nitrogen atmosphere. The solutionwas heated to 120° C. and stirred at this temperature for 6 hours. Aftercooling to room temperature, the product was filtered. A clear, liquidproduct having an acid number of 40 mg KOH/g and a viscosity of 550mPa.s was obtained.

[0067] According to ²⁹Si-NMR and ¹³C-NMR spectroscopic results, the endproduct has the following structure (III):

EXAMPLE 2

[0068] Addition reaction of hexahydrophthalic anhydride with a linearhydroxy-functional siloxane:

[0069] In a three-necked flask equipped with a coil condenser,thermometer and dropping funnel and a nitrogen connection, 226.3 g ofhexahydrophthalic anhydride and 773.7 g of a linear hydroxy-functionalsiloxane of the general formula (II) having a hydroxyl number of 130 mgKOH/g (i.e. a is 17) and a viscosity of 70 mPa.s were mixed in anitrogen atmosphere. The solution was heated to 120° C. and stirred atthis temperature for 6 hours. After cooling to room temperature, theproduct was filtered. A clear, liquid product having an acid number of115 mg KOH/g and a viscosity of 270 mPa.s was obtained.

[0070] According to ²⁹Si-NMR and ¹³C-NMR spectroscopic results, the endproduct has the following structure (IV).

EXAMPLE 3

[0071] Addition reaction of hexahydrophthalic anhydride with a linearhydroxy-functional siloxane: In a three-necked flask equipped with acoil condenser, thermometer and dropping funnel and a nitrogenconnection, 48.5 g of hexahydrophthalic anhydride and 951.5 g of alinear hydroxy-functional siloxane of the general formula (II) having ahydroxyl number of 17 mg KOH/g (i.e. a is 84) and a viscosity of 155mPa.s were mixed in a nitrogen atmosphere. The solution was heated to120° C. and stirred at this temperature for 6 hours. After cooling toroom temperature, the product was filtered. A clear, liquid producthaving an acid number of 16 mg KOH/g and a viscosity of 610 mPa.s wasobtained.

[0072] According to ²⁹Si-NMR and ¹³C-NMR spectroscopic results, the endproduct has the folowing structure (V).

[0073] For use as an additive, the carboxy-functional polysiloxanesaccording to the invention are incorporated in an amount by weight ofbetween about 0.01 and about 20% into an aqueous or solvent-containingformulation. The use of carboxy-functional polysiloxanes according tothe invention can be effected in solution or as an emulsion. Furthercomponents of the formulation, in addition to the solvent andcarboxy-functional polysiloxane in the formulation, may be, for example,emulsifiers, liquid paraffins and mineral oils.

[0074] With the use of the carboxy-functional polysiloxanes according tothe invention, an outstanding water repellant effect is achieved incombination with an improvement in the quality of handle. This ispermitted by the particular structural principle of thecarboxy-functional polysiloxanes according to the invention. The longuninterrupted siloxane chain is responsible for the characteristicproperties as a leather treatment agent. The choice of the organic unitsat the chain ends results in advantageous dissolution and emulsificationproperties for use from aqueous or solvent-containing formulations, thecarboxyl groups being capable of interacting with the positively chargedcenters on the surface of the leather.

[0075] Comparison of Performance Characteristics:

[0076] Leather water repellants are ideally applied from aqueousformulations (from 5 to 30%) using emulsifiers and standardizedconditions, such as temperature and pH.

[0077] For the determination of the water repellant effect, 5% solutionsof the compounds according to the invention (examples 1 to 3) inpetroleum ether were prepared. Leather pieces measuring 6×6 cm areintroduced for 2 hours into a screw-cap bottle which was filled with 300ml of the above solution. After the reaction time, each leather piecewas dried at 50° C. and weighed. The impregnated leather piece was thenstored in 300 ml of water for 60 min. The water absorption wasdetermined by weighing after removal of adhering water drops:

[0078] The weight difference caused by the water absorption is stated in%, based on the dry impregnated leather.

[0079] The results are shown in the following table 1: TABLE 1 AdditiveFinal weight II (%) Comparative sample, untreated 96 1 63 3 56 4 32 8 64

[0080] As is evident, the water absorptivity of leather after thetreatment with the linear carboxyfunctional organosiloxanyl derivativeaccording to the invention is substantially reduced.

[0081] The above description of the invention is intended to beillustrative and not limiting. Various changes or modifications in theembodiments described herein may occur to those skilled in the art. Thechanges can be made without departing from the scope or spirit of theinvention.

1. A linear carboxy-functional organosiloxane compound of the generalformula (I)

in which a is from 1 to 200, R¹ are identical or different aliphatic oraromatic hydrocarbon radicals, R² is—(Y)[O(C₂H_(4-b)(R³)_(b)O)_(c)(C_(d)H_(2d)O)_(e)]_(f)X, where Y is an(f+1)-valent, optionally branched hydrocarbon radical having 3 to 12 Catoms, b is from 1 to 3, c is from 0 to 20, d is from 2 to 4, e is from0 to 20, f is from 1 to 4, R³ is R¹, X is C(O)-Z-CO₂H and Z is adivalent hydrocarbon radical selected from the group consisting of

where g is from 1 to 12; R^(a) is alkyl; and y is 0 to
 4. 2. The linearcarboxy-functional organosiloxane as claimed in claim 1, wherein theradical R² is a polyether radical comprising mixed blocks.
 3. The linearcarboxy-functional organosiloxanes a claimed in claim 1, wherein R¹ is aC₁-C₅ aliphatic hydrocarbyl group or a C₆ to C₁₂ aromatic group.
 4. Thelinear carboxy-functional organosiloxane as claimed in claim 1, whereinR¹ is H and/or methyl.
 5. The linear carboxy-functional organosiloxaneas claimed in claim 1, wherein a has a value of from 10 to
 150. 6. Thelinear carboxy-functional organosiloxane as claimed in claim 1, whereinz is


7. The linear carboxy-functional organosiloxane as claimed in claim 1which has the formula

wherein R^(a) is identical or different and is a C₁-C₄-alkyl radical, R¹is methyl; a is from 1 to 150; z is 3 to 12; c is from 0 to 4; and y isfrom 0 to
 4. 8. The linear carboxy-functional organosiloxane as claimedin claim 7 wherein R^(a) is methyl and y is
 1. 9. The linearcarboxy-functional organosiloxane as claimed in claim 7 wherein R¹ isCH₃; a is from 1 to 150; z is 3 or 6; and c is 0 or 4; and y is
 0. 10. Aprocess for the preparation of linear carboxy-functional polysiloxanesas claimed in claim 1, which comprises reacting hydroxy-functionalsiloxanes of the general formula

in which a is from 1 to 200, R¹ are identical or different aliphatic oraromatic hydrocarbon radicals, R⁴ is—(Y)[O(C₂H_(4-b)(R³)_(b)O)_(c)(C_(d)H_(2d)O)_(e)]_(f)H, where Y is an(n+1)-valent, optionally branched hydrocarbon radical having 3 to 12 Catoms, b is from 1 to 3, c is from 0 to 20, d is from 2 to 4, e is from0 to 20 and f is from 1 to 4, with organic carboxylic anhydrides of thegeneral formula

in which Z is a divalent hydrocarbon radical selected from the groupconsisting of

where g is 1 to 12 R^(a) is alkyl; y is 0 to
 4. 11. A leather treatmentformulation which comprises from about 0.01 to about 50.0% by weight,based upon total weight of the formulation, of at least one linearcarboxy-functional polysiloxane as claimed in claim 1, a solvent, andoptionally an additive.
 12. The leather treatment formulation as claimedin claim 11, wherein the solvent is an aqueous solvent.
 13. The leathertreatment formulation according to claim 11 wherein the additive is anemulsifier, liquid paraffin or mineral oil.
 14. The leather treatmentformulation as claimed in claim 11 wherein the amount ofcarboxy-funtional polysiloxane is between about 0.01 to about 20% byweight.
 15. A method for providing water repellancy to leather whichcomprises applying the leather treatment formulation as claimed in claim11 to the surface of the the leather.